Anemia is common in the elderly, often as a result of known causes such as renal failure, cancer, or chronic infection. But even when patients with known causes are eliminated from consideration, hemoglobin levels decline during ageing. We will study such patients over the age of 75 and compare those whose with hemoglobin levels in the highest decile with those in the lowest decile. Patients aged 30 to 40 years will serve as controls. The elderly patients and controls will be studied for evidence of erythropoietic progenitor cell (EPC) senescence and for abnormalities of circulating erythrocytes. With circulating granulocytes serving as surrogates for EPC we will examine mtDNA and telomere length and G loop structure. Erythrocyte survival will be estimated by CO levels and red cell hexokinase activity; oxidative damage to erythrocytes will be assessed by estimating GSSG/GSH, glutathione peroxidase, carbonyl proteins, TEARS; exposure of phosphatidylserine on erythrocyte membranes will be documented. Serum IL-6 measurements and in males serum testosterone levels will be determined. Parameters that show differences between the highest and lowest deciles will be candidate causes of anemia in the elderly. If such differences also occur among controls they could account for the broad normal variation in hemoglobin levels. [unreadable] [unreadable] [unreadable]